Digital medical imaging has become increasingly important in medical imaging practice and has increased productivity for health care professionals who need to utilize images as part of patient care. It is desirable that a user be able to rapidly extract diagnostically useful information from medical images and that any user interaction with the image display be rapid, intuitive and as automated as possible.
One source of medical images is the detection of x-rays projected through a region of interest of a patient so as to measure the x-ray transmittance with an imaging detector such as used in computed radiography and direct digital radiography. Because the digital radiographic image can capture a wide range of x-ray exposures, a tone scale curve is used to selectively map input code values to output code values for presentation on a display. Because there are often regions of the image that are too dark or too light, there is a need to automatically improve the contrast and brightness in these regions without affecting the tone scale of the rest of the image. When printed films and a light box are used for the display of radiographs, an ancillary intense source of light (hot light) aids in aiding visualization of dark areas. However, the hot light is of no help in visualizing too light areas and there is no contrast enhancement in the area of interest.
When radiographic (medical) images are viewed with electronic displays, the user must adjust window width and level to improve rendering of the region of interest. This process requires skill and is time consuming and can result in sub-optimal rendering of the rest of the image. U.S. Pat. No. 5,542,003, issued Jul. 30, 1996, inventor Wofford, describes a method for automatically adjusting the window and level parameters. The commercial image editing and manipulation application Adobe Photoshop (Adobe Systems inc., San Jose, Calif.), U.S. Pat. No. 6,017,309, issued Jan. 25, 2000, inventors Washburn et al. and U.S. Pat. No. 6,047,042, issued Apr. 4, 2000, inventors Khutoryansky, et al., describe various image processing techniques that are of interest, but which do not solve the problem of rendering dark or light regions of a displayed radiographic image so that they are visually improved.
U.S. Pat. No. 6,735,330, issued May 11, 2004, inventors Van Metter et al., describes a method for automatically modifying the rendering of a digital radiographic image based on an analysis of pixel values within a selected region of interest. The method includes: providing a digital input image of digital pixel values and tone scale look-up table; creating a default rendered image by applying the tone scale look-up table to the input image; displaying the default rendered image; selecting a region of interest from the input image; computing the histogram of the pixel values within the region of interest; creating a bright light image by remapping the pixel values within the region of interest based on an analysis of the histogram and the tone scale look-up table and overlaying the bright light image on the default rendered image. While the method may solve a problem discussed above, it is desirable to provide an improved method that would address other image processing and rendering needs.